January – February – March – April – May – June – July – August – September – October – November – December
- December 3, 1824 - The Municipality of Naranjito was founded.
- December 3, 1938 - Death of Félix Córdova Dávila, politician and Resident Commissioner of Puerto Rico (b. 1878)
- December 3, 1979 - Los Macheteros opened fire on a bus carrying U.S. sailors, killing CTO1 John R. Ball and RM3 Emil E. White as well as wounding nine.
- December 4, 1979 - Eurobank was founded.
- December 5, 1916 - U.S. Congress approves the Jones Act, establishing Puerto Rico as a U.S. territory and granting U.S. citizenship to all Puerto Ricans.
- December 5, 1941 - Birth of José Aponte de la Torre, mayor of Carolina (d. 2007)
- December 9, 1897 - Birth of Tomas Blanco, writer and historian (d. 1975)
- December 11, 1929 - Birth of Axel Anderson, actor
- December 11, 1931 - Birth of Rita Moreno, Academy Award-winning actress
- December 17, 1771 - The Municipality of Cabo Rojo was founded.
- December 21, 1982 - Birth of Eddie Colón, professional wrestling
- December 22, 1936 - Héctor Elizondo, Golden Globe-nominated and Emmy Award-winning actor
- December 24, 1971 - Birth of Ricky Martin, international pop star.
- December 25, 1855 - The Municipality of Arroyo was founded.
- December 25, 1982 - Birth of Rubén Gotay, Mayor League Baseball second baseman
- December 28, 1965 - The Ponce Museum of Art is inaugurated.
- December 31, 1972 - Death of Roberto Clemente, Major League Baseball player and first Hispanic American to be selected to the Hall of Fame (b. 1934)